Question

multiply.
$(7x - 3y)(7x + 3y)$
simplify your answer.

Explanation:

Step1: Recognize difference of squares

This is of the form $(a-b)(a+b)=a^2-b^2$, where $a=7x$, $b=3y$.

Step2: Compute $a^2$

$a^2=(7x)^2=49x^2$

Step3: Compute $b^2$

$b^2=(3y)^2=9y^2$

Step4: Substitute into difference formula

$a^2 - b^2 = 49x^2 - 9y^2$

Answer:

$49x^2 - 9y^2$